Apparatus for controlling galvanic corrosion effects on a single-wafer cleaning system

ABSTRACT

A single substrate cleaning apparatus that prevents galvanic corrosion is provided. The apparatus includes a spindle configured to rotatably support a substrate. A moveable dispense arm disposed over the spindle is included. The dispense arm supports a first supply line and a second supply line. The first supply line has a first nozzle affixed to an end of the first supply line, and the second supply line has a second nozzle affixed to an end of the second supply line. The first nozzle is positioned behind the second nozzle such that a fluid dispensed from the second nozzle is dried by application of a fluid simultaneously dispensed from the first nozzle in manner that protects the substrate from galvanic corrosion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 10/013,211, filed on Dec. 7, 2001, and entitled “METHOD FORCONTROLLING GALVANIC CORROSION EFFECTS ON A SINGLE-WAFER CLEANINGSYSTEM,” which claims priority from U.S. Provisional Patent ApplicationNo. 60/305,372 filed Jul. 13, 2001 and entitled “Drying substrate usinga combination of substrate processing techniques.” Each of theseapplications is herein incorporated by reference in their entirety forall purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to semiconductor manufacturing and morespecifically to a cleaning method and apparatus for a single-wafercleaning system, which minimizes galvanic corrosion.

2. Description of the Related Art

Galvanic corrosion is induced in an environment where two dissimilarmetals are coupled through an electrolyte. One of the metals in thegalvanic cell becomes an anode and corrodes faster than it wouldnormally, while the other metal becomes a cathode and corrodes slowerthan it would normally. FIG. 1 illustrates prior art diagram 100 of abasic galvanic cell. Two dissimilar metals, 104 and 106, are coupledthrough electrolyte 102. The anode 106 donates electrons and has itscorrosion rate increased while the cathode 104 has its corrosion ratereduced.

Metal interconnects used in semiconductors are often constructed fromdissimilar metals such as Copper/Tantalum (Cu/Ta) or Copper/TantalumNitride (Cu/TaN). During cleaning operations following processingoperations such as etch and chemical mechanical planarization (CMP), thedissimilar metals are brought into electrical contact through anelectrolyte, such as water from an aqueous based cleaner or asemi-aqueous based cleaner. As a result, corrosion of one of the metalsis accelerated, thereby creating the potential for device failure. FIG.2 illustrates prior art diagram 110 depicting one example of wheredissimilar metals can form a galvanic cell. Diagram 110 illustrates adual damascene structure where trench 120 includes a via 122 down tocopper metallization line 112. Liner 114 encases copper metalizationline 112 around 3 sides and acts a copper diffusion barrier. Dielectriclayer 118 is typically a low K dielectric disposed over barrier 116. Ascan be seen in diagram 110 the via 122 is slightly misaligned overcopper metalization line 112. Consequently, two dissimilar metals areexposed, the copper of copper metallization line 112 and the liner 114since liner 114 is typically tantalum or tantalum nitride for dualdamascene applications. An additional misaligned via on a second metalline (not shown), which is not in contact with the metallization line112, can also introduce the potential for a galvanic cell once thedissimilar metals exposed in isolated lines are brought into contactthrough an electrolyte. It should be appreciated that the via need notbe misaligned as the copper can be brought into contact with a secondmetal exposed in a different region of substrate 124. Thus dissimilarmetals of even perfectly aligned structures can be brought into contactthrough an electrolyte during cleaning and rinsing operations.Additionally, while a dual damascene structure is presented in diagram110, traditional metallization processes using aluminum can also createthe potential for a galvanic cell.

During cleaning operations, substrates are exposed to cleaningchemistries. In the case of single-wafer cleaning operations thecleaning chemistries are formulated to be fast acting and thestoichiometry of the components is critical to the performance of thecleaning chemistry. For example, semi-aqueous cleaning chemicals forsingle-wafer cleaning operations typically include a solvent to removeorganic material, a chelator to enhance metal contaminant removal fromsurfaces exposed to sputtering from the etch process, and a surfactantto passivate sensitive surfaces, especially those vulnerable tocorrosion. Examples of commercially available single-wafer cleaningchemistries used for post via etch applications include NE-89 fromAshland Inc. of Dublin, Ohio and EKC 640 from EKC Technology, Inc. ofHayward, Calif.

The surfactant of the cleaning chemicals for the single-wafer cleaningoperations are formulated to help improve wetting of difficult-to-accessfeatures such as vias and contacts, and also to control galvanic effectswhere necessary, however, if the surfactant is diluted then itspassivation capacity is reduced or inhibited, thereby leaving thesubstrate more vulnerable to galvanic corrosion effects. For example,where the cleaning chemistry is puddled on the substrate and then rinsedoff with de-ionized (DI) water, the water acts as an electrolyte toinitiate the mechanism for galvanic corrosion. The galvanic corrosionmay occur within the first few seconds of rinsing, where the cleaningchemistry and the surfactant are initially diluted upon rinsing of thecleaning chemistry. The dilution of the cleaning chemistry upsets achemical equilibrium established to protect the substrate surface fromcorrosion. Since the surfactant concentration is modified by dilutionthrough rinsing, the semiconductor substrate is vulnerable to corrosionwhen the diluted surfactant concentration is insufficient to inhibitcorrosion.

FIG. 3 illustrates a prior art diagram displaying the variousconcentration gradient regions formed during the rinsing operations froma vantage point above the substrate 126. Substrate 126 is spinning inthe direction of arrow 134. Region 128 depicts the region containing thecleaning chemistry puddled onto the substrate 126 through a nozzle orother delivery mechanism (not shown). To rinse of the cleaning chemistryfrom the substrate 126, DI water is sprayed onto the substrate 126through a nozzle (not shown) directed toward the outer edge of thesubstrate 126 while the substrate is spinning. As the DI water issprayed on the substrate 126, regions of differing gradients will formon the substrate 126. Region 130 contains a mixture of the cleaningchemistry and DI water, which forms as the DI water is initially sprayedonto the substrate 126. After a period of time, enough DI water issprayed onto the substrate 126 where the cleaning chemistry is displacedand region 132 containing only DI water forms. While FIG. 3 provides asnapshot of one instance during the rinsing process, it should beappreciated that the edges of regions 132 and 130 are moving toward theedge of substrate 126 as depicted by arrows 136. The DI water rinsecontinues until eventually all of the cleaning chemistry is displacedfrom the substrate 126.

As mentioned above, region 130 includes a mixture of cleaning chemistryand DI water. Thus, the chemical equilibrium under which the cleaningchemistry is designed to function has been shifted. As a result of thedilution of the surfactant by the DI water, the corrosion protection ofthe surfactant is inhibited, which in turn exposes the substrate 126 tothe effects of galvanic corrosion. As mentioned above, the effects ofcorrosion, especially galvanic corrosion, can occur within seconds.

In view of the foregoing, there is a need to provide an apparatus andmethod to rinse the cleaning chemistry from a substrate in a mannerwhich protects the exposed metals of the substrate from galvaniccorrosion.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention fills these needs by providingan apparatus and a method which quickly removes the cleaning chemistryfrom the surface of a semiconductor substrate. It should be appreciatedthat the present invention can be implemented in numerous ways,including as an apparatus, a system, a device, or a method. Severalinventive embodiments of the present invention are described below.

In one embodiment, a method for minimizing galvanic corrosion effects ina single-wafer cleaning system is provided. The method initiates withapplying a cleaning chemistry containing corrosion inhibitors to asurface of a wafer. Then, the surface of the wafer is exposed to thecleaning chemistry for a period of time. Next, a concentration gradientat an interface of the cleaning chemistry and the surface of the waferis refreshed. Then, a rinsing agent and a drying agent are appliedsimultaneously to remove the cleaning chemistry, wherein the dryingagent dries the surface of the wafer prior to a concentration of thecorrosion inhibitors being diluted to a level insufficient to inhibitcorrosion.

In another embodiment, a method for quickly drying a surface of asemiconductor substrate is provided. The method initiates with applyinga cleaning chemistry including a surfactant to the surface of thesemiconductor substrate. Then, the surface of the semiconductorsubstrate is exposed to the cleaning chemistry for a defined timeperiod. Next, a rinsing agent and a drying agent are appliedsimultaneously to the surface of the semiconductor substrate to removethe cleaning chemistry, wherein the drying agent inhibits the rinsingagent from forming a diluted region of the cleaning chemistry fromresiding on the surface of the semiconductor substrate for a time periodsufficient to allow corrosion of the substrate.

In yet another embodiment, a chemical sequencing method for single-wafercleaning of a residue on a surface of a semiconductor substrate isprovided. The chemical sequencing method is configured to maintain aconcentration gradient at an interface between a cleaning chemistry anda residue on the semiconductor substrate. The method initiates withapplying a cleaning chemistry to the surface of the semiconductorsubstrate. Then, the cleaning chemistry is allowed to react with theresidue. Next, the cleaning agent is removed to reduce exposure of thesemiconductor substrate to corrosion. Then, the applying, the allowingand the removing steps are repeated such that the concentration gradientis refreshed to more effectively remove the residue on the surface of asemiconductor substrate.

In still another embodiment, a method for minimizing galvanic corrosioneffects in a single-wafer cleaning system while maintaining aconcentration gradient at an interface between a cleaning chemistry anda residue on a wafer is provided. The method initiates with applying thecleaning chemistry containing corrosion inhibitors to a surface of awafer. Then, the surface of the wafer is exposed to the cleaningchemistry for a period of time. Next, a concentration gradient at aninterface of the cleaning chemistry and the surface of the wafer isrefreshed. Then, the wafer is rinsed with the cleaning chemistry andsimultaneously dried with a drying agent to remove the cleaningchemistry and dry the wafer.

In another embodiment, a system for cleaning a single substrate isprovided. The system includes a spindle adapted to support the substratewhere the spindle is configured to spin the substrate. A substratesurface having a layer of a cleaning chemistry disposed thereover isincluded. A first nozzle positioned over the substrate surface is alsoincluded. The first nozzle is configured to apply a rinsing agent on thesubstrate surface while the substrate is spinning. A second nozzlepositioned over the substrate surface is included. The second nozzle isconfigured to apply a drying agent on the substrate surface while thefirst nozzle is applying the rinsing agent. A dispense arm to which thefirst and second nozzles are rigidly attached is included. The dispensearm is configured to advance radially above the substrate surface from acenter of the substrate to an edge of the substrate while the substrateis spinning and while the first and second nozzles are applying therinsing agent and the drying agent, respectively. The substrate surfaceis dried quickly to reduce exposure of the substrate surface tocorrosion. Alternative configurations can be incorporated to increasethe speed of rinsing and drying, such as incorporating multiple nozzlepairs.

In yet another embodiment, a single substrate cleaning apparatus thatprevents galvanic corrosion is provided. The apparatus includes aspindle configured to rotatably support a substrate. A moveable dispensearm disposed over the spindle is included. The dispense arm supports afirst supply line and a second supply line. The first supply line has afirst nozzle affixed to an end of the first supply line, and the secondsupply line has a second nozzle affixed to an end of the second supplyline. The first nozzle is positioned behind the second nozzle such thata fluid dispensed from the second nozzle is dried by application of afluid simultaneously dispensed from the first nozzle in manner thatprotects the substrate from galvanic corrosion.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, inwhich like reference numerals designate like structural elements.

FIG. 1 illustrates prior art diagram of a basic galvanic cell.

FIG. 2 illustrates prior art diagram depicting one example of wheredissimilar metals can form a galvanic cell.

FIG. 3 illustrates a prior art diagram displaying the variousconcentration gradient regions formed during the rinsing operations froma vantage point above the substrate.

FIG. 4 illustrates an exemplary drying system in accordance with oneembodiment of the invention.

FIG. 5 provides a detailed view of dispense nozzles positioned over asubstrate in accordance with one embodiment of the invention.

FIG. 6 illustrates a detailed diagram of the surface of the substrate inthe region where the rinsing agent and drying agent are impinging on thesurface of the substrate to remove a cleaning chemistry layer inaccordance with one embodiment of the invention.

FIG. 7 illustrates a diagram providing a detailed view of the interfacebetween the substrate and the cleaning chemistry layer in accordancewith one embodiment of the invention.

FIG. 8 illustrates a flowchart depicting a method for minimizinggalvanic corrosion effects in a single-wafer cleaning system inaccordance with one embodiment of the invention.

FIG. 9 illustrates a flowchart depicting a chemical sequencing methodfor single-wafer cleaning of a residue on a semiconductor substrate inaccordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An invention is described which provides a method and apparatus forremoving a cleaning chemistry from the surface of a semiconductorsubstrate without exposing the substrate to corrosion effects during asingle-wafer cleaning operation. In addition, the method and apparatusprovide a more effective means for removing the residue during cleaningoperations without increasing the consumption of the cleaning chemistry.It will be obvious, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order not to obscure the present invention.

The embodiments of the present invention provide a method and apparatusfor applying and removing a cleaning agent from a semiconductorsubstrate without exposing the substrate to galvanic corrosion effects.In one embodiment, the precisely formulated cleaning chemistry appliedto the semiconductor substrate is removed in a manner to reduce dilutionof the components of the cleaning chemistry. In another embodiment, thecleaning chemistry includes a surfactant to inhibit corrosion. As usedherein, surfactant also refers to corrosion inhibitors. The cleaningchemistry is removed from the surface of the semiconductor substrate ina manner where the dilutive effects of the rinsing agent arecounteracted by quickly removing the cleaning chemistry from the surfaceof the substrate. By quickly drying the surface of the substrate duringthe rinsing process, the semiconductor remains protected from corrosion.

In addition, a method and apparatus for more effectively removing thecleaning chemistry from the surface of the semiconductor substrateduring single-wafer cleaning is provided in another embodiment. The fastacting formulations of the cleaning chemistries for single-wafercleaning processes perform optimally when a concentration gradientbetween the cleaning chemistry and the residue to be removed at thesurface of the semiconductor substrate is maintained by removal of theboundary layer formed from reaction of the cleaning chemistry with theresidue. More particularly, the retarding effects of the reactantspecies produced by the interaction of the cleaning chemistry and theresidue is minimized by a chemical sequencing process to refresh thecleaning chemistry in order to maintain the concentration gradient. Therefreshing process can include removing cleaning chemistry from thesurface of the substrate and replacing it with fresh cleaning chemistryor continually recycling the cleaning chemistry to maintain theconcentration gradient as will be discussed in more detail below.

FIG. 4 illustrates an exemplary drying system 140 in accordance with oneembodiment of the invention. The drying system 140 includes a hollowspindle 142 configured to hold a substrate 148 and disposed within andover a drip tray 150. Dispense arm 152 is positioned over a top surfaceof the substrate 148. Dispense arm 152 is supported by dispense armsupport post 154 which is mechanically connected (not shown) to adispense arm drive shaft (not shown) disposed within a dispense armdrive shaft housing 156. Substrate 148 is affixed to hollow spindle 142with fingers 158. Hollow spindle 142 is configured to rotate, which inturn rotates the substrate 148. Spindle motor 160 is configured toprovide rotational energy which is applied to hollow spindle 142 withdrive belt 162, which spins the substrate 148 locked to the hollowspindle 142 in fingers 158.

Surrounding hollow spindle 142, fingers 158, and substrate 148 is sprayshield 164. Spray shield 164 is configured to contain any liquid fromthe rinsing and drying process to the region around hollow spindle 142.In one embodiment of the invention, spray shield 164 is configured witha door (not shown) that is magnetically coupled to a semi-circularpneumatic system to provide lateral access to the hollow spindle 142 forthe insertion and removal of substrates 148.

In another embodiment of the invention, a rinsing agent and a dryingagent are simultaneously applied to the top surface of substrate 148.The rinsing agent is applied through nozzle 166 and the drying agent isapplied through nozzle 168 in one embodiment. Examples of rinsing agentsinclude de-ionized water (DIW) and Isopropyl alcohol. Examples of dryingagents include isopropyl alcohol (IPA), IPA vapor, heated Nitrogen (N₂)gas, and other inert gasses or vaporized chemicals. Some drying agentsproduce by-products or result in excess vapors that can become trappedwithin drip tray 150. An exhaust 170 is provided for the release ofairborne chemicals or vapors, and a drain 172 is provided to drain anyliquid residue of both cleaning and drying agents.

Dispense arm 152 provides for the supply of rinsing and drying agentsthrough dispense nozzles 166 and 168 through corresponding supply lines174 and 176 to substrate 148 positioned in fingers 158 on the hollowspindle 142. The drying agent and the rinsing agent are supplied fromseparate reservoirs (not shown) and are routed along dispense arm 152 todispense nozzles 168 and 166, respectively. Nozzles 166 and 168 directstreams of drying agent and the rinsing agent to a top surface ofsubstrate 148.

In one embodiment, positioning of the dispense arm 152 across the topand surface of substrate 148 is controlled by a dispense arm controller(not shown) and a dispense arm drive shaft (not shown) contained withina dispense arm drive shaft housing 156. The dispense arm drive shaft ismechanically connected to the dispense arm support post 154 providing adirect mechanical connection between the drive shaft and the dispensearm 152 to position the dispense arm 152. The dispense arm 152 isconfigured to pivot about the dispense arm support post 154 to move thedispense arm 152 and move the dispense nozzles 166 and 168 radiallyacross a top surface of a substrate. In one embodiment of the invention,the rinsing and drying agents are dispensed along a radius of a spinningsubstrate from a center region of the substrate to a peripheral regionof the substrate. The dispense arm 152 is therefore moved along thesurface of the spinning substrate from the center region outward to aperipheral region. In another embodiment, the nozzles 166 and 168 arepositioned so that the drying agent is applied to the surface of thesubstrate directly behind the rinsing agent as the dispense arm 152traverses across the surface of the substrate 148. As will be describedin more detail below, applying the drying agent simultaneously with therinsing agent and in a manner which quickly dries the surface of thesubstrate 148 in a single-wafer cleaning operation protects thesubstrate from corrosion effects. It should be appreciated that FIG. 4is provided as an exemplary illustration of one embodiment of anapparatus and not meant to be limiting.

FIG. 5 provides a detailed view of dispense nozzles 166 and 168positioned over substrate 148 in accordance with one embodiment of theinvention. Dispense arm 152 traverses a path radially across the surfaceof the substrate 148 in a plane above the substrate as indicated byarrow 180. Therefore, as the substrate 148 is spinning about its axis,nozzles 166 and 168 are directing a flow of rinsing agent and a flow ofdrying agent across the surface of the substrate 148. By rinsing thecleaning chemistry and immediately drying the surface of the substrate148, the corrosion inhibitors of the cleaning chemistry do not remain onthe surface of the substrate 148 in a diluted state unable to inhibitcorrosion effects. Since galvanic corrosion can be initiated in a matterof seconds, the immediate drying of the substrate reduces or preventsthe onset of the corrosion effects as the substrate is quenched asdescribed above.

FIG. 6 illustrates a detailed diagram of the surface of the substrate148 in the region where the rinsing agent 182 and drying agent 184 areimpinging on the surface of the substrate 148 to remove a cleaningchemistry layer 188 in accordance with one embodiment of the invention.Rinsing agent 182 is applied through dispense nozzle 166 simultaneouslywhile drying agent 184 is applied through dispense nozzle 168. In oneembodiment, the nozzles 166 and 168 are positioned so that the fluidstreams 190 and 192, emanating from nozzles 166 and 168, respectively,are directed at an angle to the surface of the substrate 148 and in thesame plane as the direction of the movement 180 of the dispense arm. Therinsing agent 182 is applied ahead of the drying agent 184 to a topsurface the spinning substrate 148 while moving from a center region ofthe substrate 148 towards a periphery region of the substrate 148. Therinsing agent is configured to rinse the surfaces of the substrate 148to remove the cleaning chemistry layer 188. In one embodiment, therinsing agent is DIW. The drying agent is formulated such that itreduces the surface tension of the rinsing agent and the movement of theliquid and residue is enhanced thereby drying the surfaces of thesubstrate quickly, without allowing a diluted region of the cleaningchemistry layer to remain on the surface of the substrate 148.

It should be appreciated that by simultaneously applying the dryingagent 184 and the rinsing agent 182 of FIG. 6, the substrate surface isquickly dried so that any region containing a mixture of the cleaningchemistry and the rinsing agent 182 is minimized. Moreover, bysimultaneously applying the rinsing agent 182 and the drying agent 184,the surface of the substrate 148 is quickly dried. Therefore, even ifthe diluted region of the cleaning chemistry is formed, it is quicklydried without allowing the opportunity for corrosion effects toinitiate.

FIG. 7 illustrates a diagram providing a detailed view of the interface194 between the substrate 148 and the cleaning chemistry layer 188 inaccordance with one embodiment of the invention. Substrate surface 196contains a residue from a previous operation, such as etch or CMP in oneembodiment. During a single-wafer cleaning operation, the cleaningchemistry applied to the substrate surface 196 is configured to quicklydissolve the residue to enable rinsing the residue from the surface ofthe substrate. The cleaning chemistry typically includes at least asolvent to dissolve organic materials, a chelator to dissolve metals anda surfactant to inhibit corrosion. As mentioned above, the cleaningchemistry is precisely formulated for the single-wafer cleaning processto be fast acting. The pH, concentration of the chemical species and theconcentration of water of the semi-aqueous cleaning chemistries arecarefully formulated to provide the desired cleaning result.Additionally, the reactions taking place at the interface 194 occur inseconds.

Therefore, at the interface 194 of FIG. 7 as the cleaning chemistry isdissolving or reacting with the residues from a previous operation, thechemical equilibrium is shifted, which in turn retards the activity ofthe cleaning chemistry. The reactant species resulting from the chemicalreactions occurring at the interface 194 reduces the concentrationgradient between the active chemicals of the cleaning chemistry and theresidue with which the cleaning chemistry is interacting. Therefore, inanother embodiment of the invention, a chemical sequencing method isemployed to refresh the concentration gradient. As will be explained inreference to FIG. 9, the chemical sequencing operation includes applyingthe cleaning chemistry to the substrate for a specified time period,quickly removing the cleaning chemistry as discussed above withreference to FIGS. 4-6 and repeating the applying and removing. In thisembodiment, while the cleaning chemistry is applied at least twice, theabsolute amount of cleaning chemistry used is not increased. Forexample, where the cleaning chemical is applied twice, each applicationuses half the amount as when the cleaning chemistry is applied once asexplained in reference to FIG. 9. In another embodiment, the cleaningchemistry is recycled, i.e., as it is removed from the surface of thesubstrate it is captured and re-applied to the surface of the substrate.It should be appreciated that as the cleaning chemistry is continuouslysprayed on the surface of the substrate, the concentration gradientremains substantially constant.

FIG. 8 illustrates flowchart 198 depicting a method for minimizinggalvanic corrosion effects in a single-wafer cleaning system inaccordance with one embodiment of the invention. Flowchart 198 initiateswith operation 200 where a cleaning chemistry is applied to the wafer(also referred to as a semiconductor substrate). In one embodiment thecleaning chemistry includes a surfactant for inhibiting corrosion. Inanother embodiment, the surfactant protects the wafer from galvaniccorrosion. One skilled in the art would appreciate that the cleaningchemistry can be puddled in a bulk application or sprayed on the wafercontinuously. The method then advances to operation 202 where the waferis exposed to the cleaning chemistry for a defined period of time. Inone embodiment, the cleaning chemistry for a single-wafer cleaningmethod is designed to dissolve the residues between about 30 seconds toabout one minute. The method then proceeds to operation 204 where aconcentration gradient is refreshed. Here, the gradient between thecleaning chemistry and the residue at an interface of the wafer isrefreshed by continuously spraying the cleaning chemistry onto thesurface of the wafer in one embodiment. In another embodiment, thecontinuously sprayed cleaning chemistry is collected as it falls off thesurface of the spinning wafer and recycled. For example, the drip trayof FIG. 4 can collect the cleaning chemistry for recycling. In anotherembodiment, the concentration gradient is refreshed through a chemicalsequencing process where the cleaning chemistry is puddled or sprayedonto the substrate for a period of time and then removed. Fresh cleaningchemistry is then applied again to the substrate to refresh theconcentration gradient.

The method of FIG. 8 then advances to operation 206 where a rinsingagent and a drying agent are applied simultaneously to the surface ofthe wafer to remove the cleaning chemistry. In operation 206 thecleaning chemistry is removed quickly i.e., without allowing a dilutedregion of surfactant to remain on the wafer for a period of time whichallows for corrosion to occur on the wafer. In one embodiment, therinsing agent and the drying agent are applied as discussed with respectto FIGS. 4-6. In another embodiment, the rinsing agent is one of DIW, orany other liquid which can displace and quench the cleaning chemistrysuch as isopropyl alcohol, and the drying agent is one of IPA, IPAvapor, nitrogen, heated nitrogen or other inert gas.

FIG. 9 illustrates flowchart 208 depicting a chemical sequencing methodfor single-wafer cleaning of a residue on a semiconductor substrate inaccordance with one embodiment of the invention. The method initiateswith operation 210 where a cleaning chemistry is applied to a surface onthe semiconductor substrate. In one embodiment, the cleaning chemistryis one of NE-14 and NE-89 from Ashland Inc. of Dublin, Ohio and EKC 640from EKC Technology, Inc. of Hayward, Calif. In another embodiment, thesingle-wafer cleaning method is being applied after an etch or CMPoperation which leaves residues on the surface of the semiconductorsubstrate. The method then advances to operation 212 where the cleaningchemistry is allowed to react with the residue on the surface of thesemiconductor substrate. Here, the cleaning chemistry resides on thesurface of the wafer for a defined period of time to dissolve theresidue. In one embodiment, the defined period of time is between about30 seconds and about one minute.

The method of flowchart 208 then moves to operation 214 where thecleaning chemistry is removed quickly to reduce exposure of thesemiconductor substrate to corrosion. In one embodiment, the cleaningchemistry is removed quickly as described in reference to FIGS. 4-6where a rinsing agent and a drying agent are simultaneously applied tothe surface of the semiconductor substrate to remove the cleaningchemistry. The method then advances to operation 216 where operations210, 212 and 214 are repeated. The concentration gradient is refreshedby repeating operations 210, 212 and 214, so that the activity of thecleaning chemistry is not diminished by the build-up of reactant speciesat the interface between of the cleaning chemistry and the surface ofthe semiconductor substrate. As described with reference to FIG. 7, areactant species resulting from the chemical reactions occurring at theinterface reduces the concentration gradient between the activechemicals of the cleaning chemistry and the residue with which thecleaning chemistry is interacting. Thus, the chemical equilibrium underwhich the cleaning chemistry is most effective is shifted by thisbuild-up.

By refreshing the cleaning chemistry, the optimal chemical equilibriumis re-established. In one embodiment, the method of flowchart 208consumes substantially the same amount of cleaning chemistry as a singleapplication process. More specifically, if the single applicationprocess consumes about 10 ml to about 100 ml, then the chemicalsequencing operation where the cleaning chemistry is removed once andre-applied consumes half the amount for each application i.e., betweenabout 5 ml to about 50 ml. Therefore, the absolute quantity of cleaningchemistry consumed does not increase. Additionally, the total amount oftime for the single-wafer cleaning method of flowchart 208 issubstantially the same as for a single application of the cleaningchemistry. Since the concentration gradient is refreshed, the summationof the residence time for the cleaning chemistry for each application ofthe chemical sequencing method is substantially similar to the singleapplication residence time. For example, the processing time for achemical sequencing operation where the cleaning chemistry is applied,then removed and re-applied is substantially similar to the processingtime of a single application of the cleaning chemistry. That is, thecleaning chemistry for the chemical sequencing is applied twice,however, each application has a residence time of about half of theresidence time for the single application, since the gradient isrefreshed in between applications during chemical sequencing. Therefore,the total processing time remains substantially similar.

It should be appreciated that more than two applications of the cleaningchemistry may be utilized. For example, the cleaning chemistry may beapplied three or more times in one embodiment. In this embodiment, theamount of cleaning chemistry consumed remains substantially similar aswell as the processing time when compared to the single application. Inanother embodiment, the cleaning chemistry can be continually applied tothe surface of the semiconductor substrate. Here, the cleaning chemistrysprayed or puddled onto the surface of the substrate is recycled as itis removed from the substrate surface. In this embodiment theconcentration gradient would be continually refreshed.

In yet another embodiment of the invention, the cleaning chemistry isapplied to the substrate using the apparatus of FIGS. 4-6. Here, thecleaning chemistry is applied to the surface of the substratesimultaneously with the drying agent i.e., the cleaning chemistryreplaces the rinsing agent. For example the cleaning chemistry isinitially applied to the substrate and exposed to the substrate for aperiod of time. Here the cleaning chemistry can be puddled, sprayed orcontinuously sprayed and recycled for a period of time as discussedabove. In the continuous spray mode, the cleaning chemistry is recycledto refresh the concentration gradient continuously in one embodiment.After the period for the exposure is complete the cleaning chemistry isrinsed form the wafer using the apparatus as described in reference toFIGS. 4-6. In one embodiment, the cleaning chemistry replaces DI wateror any liquid which is used to displace and quench the cleaningchemistry as a rinsing agent.

For the embodiment where the cleaning chemistry replaces the rinsingagent discussed above, it should be appreciated that the cleaningchemistry will be easily captured and recycled if desired. In turn, thewaste effluent quantity would be reduced as the cleaning chemistry isnot diluted with DI water or other rinsing agent, thus the cleaningchemistry can be recycled and reused. Furthermore, galvanic corrosioneffects would be minimized as the cleaning chemistry is not diluted bythe rinsing agent. Therefore, the chemical equilibrium established forthe surfactants or corrosion inhibitors of the cleaning chemistry ismaintained and refreshed to control galvanic corrosion effects.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

1. A system for cleaning a single substrate, the system comprising: aspindle adapted to support the substrate, the spindle configured to spinthe substrate; a substrate surface having a layer of a cleaningchemistry disposed thereover; a first nozzle positioned over thesubstrate surface, the first nozzle configured to apply a rinsing agenton the substrate surface while the substrate is spinning; a secondnozzle positioned over the substrate surface, the second nozzleconfigured to apply a drying agent on the substrate surface while thefirst nozzle is applying the rinsing agent; a dispense arm to which thefirst and second nozzles are rigidly attached, the dispense armconfigured to advance radially above the substrate surface from a centerof the substrate to an edge of the substrate while the substrate isspinning and while the first and second nozzles are applying the rinsingagent and the drying agent, respectively, wherein the substrate surfaceis dried to reduce exposure of the substrate surface to corrosion. 2.The system of claim 1, wherein the cleaning chemistry includes a solventand a chelator.
 3. The system of claim 1, wherein the corrosion reducedis galvanic corrosion.
 4. The system of claim 1 further comprising: aspray shield surrounding the spindle.
 5. The system of claim 4, whereinthe spray shield provides access to the substrate.
 6. A single substratecleaning apparatus that prevents galvanic corrosion, comprising: aspindle configured to rotatably support a substrate; a moveable dispensearm disposed over the spindle, the dispense arm supporting a firstsupply line and a second supply line, the first supply line having afirst nozzle affixed to an end of the first supply line, the secondsupply line having a second nozzle affixed to an end of the secondsupply line, the first nozzle positioned behind the second nozzle suchthat a fluid dispensed from the second nozzle is dried by application ofa fluid simultaneously dispensed from the first nozzle in manner thatprotects the substrate from galvanic corrosion.
 7. The apparatus ofclaim 6, wherein the dispense arm is configured to traverse over asurface of the substrate.
 8. The apparatus of claim 6, wherein thedispense arm is configured to traverse over a surface of the substratefrom a center region of the substrate to a peripheral region of thesubstrate.
 9. The apparatus of claim 6, further comprising a supportpost connected to the dispense arm, the dispense arm configured to pivotabout the support post, thereby driving the first and second nozzlesradially over the surface of the substrate.
 10. The apparatus of claim6, further comprising: a spindle motor providing rotational energy tothe spindle through a belt operably connecting the spindle and thespindle motor.
 11. The apparatus of claim 6, further comprising: a driptray disposed around and below the spindle.
 12. The apparatus of claim6, wherein the first and second nozzles are configured to direct fluidstreams therefrom at an angle relative to a surface of the substrate.13. The apparatus of claim 12, wherein the angle causes the fluidstreams to be directed towards an outer edge of the substrate when thefirst and second nozzles are disposed over an inner region of thesubstrate.
 14. A single substrate cleaning apparatus, comprising: arotatable substrate support; a dispense arm moveably disposed over thesubstrate support, the dispense arm moveable in a plane substantiallyparallel to a top surface of the substrate support, the dispense armsupporting multiple fluid delivery lines, each of the fluid deliverylines having a nozzle affixed to corresponding ends of the fluiddelivery lines; a post providing support for the dispense arm to pivotaround; and a drip tray encircling at least a bottom surface of thesubstrate support.
 15. The apparatus of claim 14, further comprising: amotor providing rotational energy to the substrate support through abelt operably connecting the motor and the substrate support.
 16. Theapparatus of claim 14, wherein the drip tray includes a vent and adrain.
 17. The apparatus of claim 14, wherein each nozzle is oriented ina same plane thereby enabling a first nozzle to apply a rinsing agentand a second nozzle behind the first nozzle to simultaneously apply adrying agent so as to minimize conditions conducive to galvaniccorrosion.
 18. The apparatus of claim 17, wherein each nozzle isconfigured to direct a fluid stream at an angle to a surface of thesubstrate support in a direction of movement of the dispense arm.